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its southern range it extends to Lower California or 

 western Mexicoo It is said to be characterized by a 

 southern submergence, which means that species existing 

 in shallow waters to the north, occur at greater depths 

 farther to the south (southern and Lower California), 

 because of gradually rising surface temperatureSo 

 Furthermore, the endemic (native) element in the temperate 

 fauna of the North American Pacific Ocean is believed 

 to be developed to the extent that endemic species 

 constitute at least half of all species in the various 

 animal groupSo These conclusions were reached from 

 studies based largely on hard-shelled mollusks, echinoderms, 

 and fishes coming mainly from parts of central California 

 and northwardo Applications to southern California is 

 therefore limited except to deeper waters, because the 

 surface temperatures are much higher « In the basin 

 systems of southern California there are perhaps barriers 

 of unknown quantities and kinds, and in Santa Monica 

 Bay there are additional variables resulting from possible 

 effects of pollutiono It is difficult, therefore, to 

 find parallel studies. In the best studied groups of 

 metazoan invertebrates (mollusks and echinoderms) there 

 are many specific names, referrring to geographic locations 

 of southern California, which suggests that these species 

 are endemic to these places. 



Some comparisons were made with quantitative samples 

 taken from shallow bottoms near Acapulco, Mexico (collected 



